<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .tagger{
            height: 100px;
            width: 200px;
            border: 2px solid black;
            position: relative;
        }
        .tagger::after{
            content: "";
            width: 100px;
            height: 100px;
            background-color: cadetblue;
            
            position: absolute;
            left:0;
        }
        .tagger:hover{
            
        }
        .tagger:hover::after{
            left:calc(100% - 100px);
            transition: left 1s ease;
            
        }
    </style>
</head>
<body>
    <div class="tagger"></div>
</body>
</html>